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May 21, 1963
J. R. HARKNESS
3,090,875
THERMOELECTRODYNAMIC PRIME MOVERS
Filed April '7, 1960
V
I6
s Sheets-Sheet 1
3
27
28
J'use 21R.Harknass
33 343%
*9‘ MM?“
May 21, 1963
J. R. HARKNESS
3,090,375
THERMOELECTRODYNAMIC PRIME MOVERS
Filed April 7, 1960
3 Sheets-Sheet 3
Joseph R.Harkness
United States Patent Ofice
3,090,875
Patented May 21, 1963
2
3 (I90 875
THERMDELEQjTRQ?YN’AQMIC PREIVEE MOVERS
Joseph R. Harimess, Milwaukee, Wis, assignor to Briggs
& Stratton Corporation, Milwaukee, Win, a corporation
of Belaware
Filed Apr. '7, 196%, Ser- N . 126L662
14 Claims. (ill. 310-4)
In this same connection it is also an object of this in
vention to provide a thermoelectrodynamic prime mover
which advantageously incorponates a known motor that
is suitable for energ-ization from a low voltage high cur
rent D.C. source.
While motors are known that are suitable for energiza
tion by the low voltage high current output of a thermo
couple or thermopile, such motors are neither inexpen
sive nor compact, and therefore they would not be suit
movers and refers more particularly to devices of the type 10 able ~for a portable or mobile thermoelectrodynamic
prime mover.
comprising a thermocouple or thermopile, and an electric
It is therefore another object of this invention to pro
motor connected with such a thermoelectric current gen
vide a novel motor adapted to be energized by low ‘voltage
erating device for energization thereby.
This invention relates to thermoelectrodynamic prime
Recent progress in the development of thermocouples
direct current and which is compact, low in cost, simple
and \thermopiles has oifered the possibility of using such 15 in construction and e?icient in ‘operation.
a device as a component of a prime mover comprising a
heat source, a thermocouple or thermopile exposed to
heat from the source and to cooling air, and an electric
motor connected with the thermocouple {for energization
by current which the thermocouple generates as a result
of the temperature difference across it. Such a machine
In connection with the last stated object, it is a fur
ther object of this invention to provide a low voltage
DC. motor that is very well adapted, by reason of the
shape and arrangement of its parts, to comprise an ele
ment of a relatively compact ‘and inexpensive thermo
electrodynarnic prime mover.
With the above and other objects in view which will
appear as the description proceeds, this invention resides
in the novel construction, combination and arrangement
is extremely quiet in operation and requires almost no
maintenance, but to be suitable for powering portable
equipment, and even lfOl‘ many stationary applications,
it must be reasonably inexpensive, light, compact and 25 of parts substantially as hereinafter described and more
particularly de?ned by the appended claims, it being un
e?'icient.
In general it is the object of the present invention to
derstood that such changes in the precise embodiments
provide a thermoelectrodynamic prime mover having to
of the hereindisclosed invention may be made as come
a marked degree the attributes of low cost, lightness,
within the scope of the claims.
The accompanying drawings illustrate several com
compactness and ei?ciency, and which is therefore par 30
ticularly well suited for use in applications where small
plete examples of physical embodiments ‘of the invention
internal combustion engines have heretofore been em
constructed according to the best modes so far devised
ployed.
for the practical application of the principles thereof, and
More speci?cally, it is an object of this invention to
in which:
provide a thermoelectrodynamic prime mover of the 35
FIGURE ‘1 is 1a vertical sectional view of a thermo
character described wherein the components of the ma
electrodynamic prime mover embodying principles of
chine are associated with one another in an arrangement
this invention, taken on the axis of the machine;
which affords great compactness, particularly by reason
FIGURE 2 is a fragmentary vertical sectional view of
of the provision of an annular thermocouple, a motor
a modi?ed form of the prime mover of this invention,
energized by the thermocouple and disposed coaxially 40 incorporating a somewhat different type of electric motor;
with the thermocouple, ‘and a fan for cooling the cold
FIGURE 3 is a vertical sectional view of a thermo
junction of the thermocouple which is coaxially driven
electrodynamic prime mover incorporating another suit
by the motor.
able type of motor;
Other objects of this invention relate to the problems
FIGURE 4 is a horizontal sectional view taken on the
posed by the characteristic low voltage output of thermo 4.5 plane of the line 4-4 in FIGURE 3;
couples and thermopiles. Although the current gener
ated by a thermocouple is substantially in proportion to
its size and is therefore limited only by practical consid
erations, the voltage of the output is very low, even
FIGURE 5 is a top view on a reduced scale of a type
of thermopile suitable for use in the prime mover shown
in FIGURE 3; and
FIGURE 6 is a vertical sectional view of a modi?ed
when individual thermocouples are connected in series 50 embodiment of the motor shown in FIGURES 3 and 4.
in a thermopile, unless the thermopile comprises an in
Referring now to the accompanying drawings, in which
ordinately large number of thermocouples. It has been
thought heretofore that practical utilization of the output
of thermocouples required the provision of ‘an inverter
like numerals designate like parts throughout the several
views, the numeral 5 designates generally a thermoelectro
dynamic prime mover embodying the principles of this
or the like for stepping up voltage, but any device for 55 invention and which comprises, in general, a substan
voltage step-up increases the size, weight and complexity
tially annular thermopile ‘6, the axis of which is upright,
of the prime mover without ‘actually improving its overall
e?iciency. However, if the low voltage DC output of
a coaxial heat source 7 which cooperates with the thermo
thus minimizing electrical transmission losses.
sidered the terminals of the thermocouples comprising
pile, a low voltage motor 8 coaxially mounted beneath the
a thermocouple or thermopile is to be delivered directly
thermopile, and a fan 9 coaxially mounted on the shaft
to a motor, the conductors for transmitting electrical 60 1% of the motor, between the motor and the thermopile.
energy from the thermocouple to the motor must have
The annular thermopile 6 comprises an inner ring 48
very low losses and the motor must be of a type that
of
one kind of metal, 1a plurality of spoke-like elements
can operate efficiently with low voltage, high current
49 of a semiconductor material such as lead telluride or
energization.
With the foregoing considerations in mind, it is an 65 bismuth telluride, and an outer metal ring 50. The radi
ally extending spoke-like elements abut the inner ring at
other object of this invention to provide a thermoelectro
their inner ends, to provide a hot junction 11, and abut
dynamic prime mover which requires no inverter or other
the outer ring at their outer ends to provide a cold junc
voltage step-up means, and wherein the arrangement of
tion 12, ‘and the
produced by the thermopile is
the thermocouple or thermopile ‘and the motor energized
by it is so compact as to permit very short conductors to 70 dependent upon the di?erence in temperature between the
two junctions. The inner and outer rings may be con
be used for connecting the current source with the motor,
3,090,875
3
the thermopile, since a potential difference between them
is manifested when the thermopile is in operation.
Cooling ?ns 13 integral with the outer ring 50 and pro
jecting radially outwardly therefrom serve to carry heat
away from the cold junction. The hot junction is heated 5
by the heat source 7, which consists of a suitable burner
4
inwardly, and an axially magnetized annular permanent
magnet 32 secured to the inner face of one leg 34 of the
core. The inner face of the permanent magnet ‘and the
inner face of the other leg 35 of the core provide the
pole pieces 2'3 which de?ne the air gap into which the
rotor projects radially a substantial distance and across
14 concentrically mounted in the thermopile, near its
which the ?ux path extends parallel to the axis of the
bottom. The burner 14 is connected by a duct 15 lWlfh a
source of combustible fuel, which may be either liquid
or gas, and a valve 16 in the duct 15 provides for adjust
ment of the rate of fuel ?ow to the burner to thus provide
rotor shaft It).
The ?eld means is supported on brackets 36, which hold
generated by the thermopile.
it spaced above the mounting platform 25 to provide a
passage by which cooling air may ?ow inwardly to the
underside of the rotor. Rigid insulating supports 37 fas~
Obviously suitable provision is also made for the intro
duction of combustion air into the duct 15. The inner
pile hold the thermopile concentrically spaced above the
for control of the
tened to the core 31 and the outer ring 56 of the thermo
ring 48 of the thermopile serves as a due for the burner, 15 ?eld core to provide room for the fan. Also secured to
the ?eld core are insulating supporting members 53 that
carry conventional brush holders 3:8 in which the brushes
jecting ?ns 51 for e?icient conduction of heat to the hot
21 are mounted in sliding engagement with the rotor pe
junction.
and may be provided with integral radially inwardly pro
With any of the known thermopiles, the
pro
duced in consequence of the temperature difference be
tween the hot and cold junctions has a very low voltage
which may be on the order of .1 or .2 volt per thermo
couple, but may have very substantial current values.
The coaxial mounting ‘of the motor directly beneath the
riphery. Apertures 39 in the upper leg 35 of the core
permit the conductors 17 to extend from the outer ring
of the thermopile to the brushes.
For e?’iciency a homopolar motor must have a relatively
large number of brushes spaced circumferentially around
the peripheral portion of its rotor, and the brushes must
thermopile simpli?es electrical connection of the thermo
have as much area as possible in contact with the rotor
pile ‘to the motor, as brought out hereinafter, and results
in electrical transmission losses which are negligible.
To afford desirable compactness in the machine, the
motor is of the type that has a ?at, disc-like rotor 18 and
a stator comprising ?eld means 19 having pole pieces as
that lie adjacent to and face opposite surfaces of the rotor
to de?ne an axially extending air gap. In the embodiment
of the prime mover of this invention illustrated in FIG
URE 1, the motor is of the known homopolar type,
to minimize their contact resistance.
which, besides being satisfactorily compact, is well adapted
for energization from a low voltage source. The rotor
in this machine is a ?at disc of copper, aluminum or simi
lar conductive material, coaxially secured and electrically
connected to the shaft 16‘ and engaged at its periphery by
a number of brushes 21.
The shaft is grounded to the
inner ring 48 of the thermopile, as hereinafter described,
and conductors 17 connect the outer ring 50 of the ther
mopile with the brushes 21.
The fan or impeller 9' is coaxially secured to the motor
shaft, between the motor and the thermopile, so that the
fan rotates with the shaft when the machine is operating,
blowing cooling air upwardly across the cooling ?ns 13
on the thermopile to dissipate heat from them and thus
promote cooling of the cold junction of the thermocou
ples. An axially deep ba?ie ring 51 around the radially
outer edges of the cooling ?ns, preferably formed in
tegrally with them, guides the ?olw of such air across the
fins. A series of circumferentially spaced apart aper
tures 23 may be provided in the rotor disc 18, spaced
a short distance outwardly from the shaft, to permit cool
ing air to flow upwardly to the fan, and it will be appar
ent that the air drawn through these apertures also serves
to cool the rotor.
A bearing cage 24 mounted on a platform 25 and pro
But the brushes
naturally produce frictional drag, the magnitude of which
is substantially in proportion to the linear speed of the
rotor surface engaged by the brushes. The embodiment
of the invention shown in ‘FIGURE 2 is intended to have
lower brush friction than that just described, by reason of
the location of the brushes relatively close to the rotor
axis, so that the linear speed of the rotor relative to the
brushes is comparatively low for a given rate of rotor
rotation.
The thermopile in the prime mover shown in FIGURE
2 is similar to that described above, except that its outer
ring 150 extends axially downwardly to the mounting plat
form 25 to provide both a support for the thermopile and
an electrical grounding connection with the metal plat
form. The upright shaft 16.‘! of the motor is medially
journaled and supported in bearings 26 in a bearing cage
24 carried by the platform, as in the previously described
embodiment of the invention, and is insulated from the
bearings, and hence from the platform, by means of an
insulating sleeve 54'.
The fan 9 is coaxially secured to the shaft, between the
motor and the thermopile, but in this instance the fan
supports the rotor 118 by means of stud-like connectors
59 projecting downwardly from the outer ends of the fan
blades and secured to the rotor near its periphery, and
the rotor is annular and has an axially upwardly project
ing ?ange 60 around its inner circumference against which
the brushes 21 engage. The brushes 21 may be supported
by conductive holders 128 which are secured to and thus
electrically connected with the platform 25, to thereby
connect the brushes 21 with the outer ring 150‘ of the
thermopile. The circuit through the rotor is completed
through brushes 29‘ mounted on the underside of a burner
plate 30 which is conductingly connected to
vided with bearings 26 supportingly journals the medial 60 supporting
the inner ring 48 of the thermopile, and engaging a con
portion of the shaft 10; and the lower end portion 27
tact plate 29' on the top of the shaft, as in the previously
of the shaft, which projects through an aperture 28‘ in
described embodiment of the invention.
the platform, provides a power take off for the machine.
It will be observed that the inner edge of the annular
Preferably the shaft is insulated from the platform 25
and the ?eld means 19 by an insulating bushing 54 in
the bearing cage. At its upper end the shaft carries a
contactor plate 29' slidingly engaged by brushes 29‘ which
project downwardly from the under side of a brush holder
plate 30 ?xed to the bottom of the ?ue-like inner ring of
the thermopile to thus electrically connect the shaft 10
to the thermopile. The brush holder plate may also pro
rotor is radially spaced a substantial distance from the
shaft 10, and the annular ?eld means 110 is “inside out”
relative to that in the FIGURE 1 embodiment of the in
vention, that is its legs 134 and 135 extend radially out
wardly to de?ne a radially outwardly opening air gap,
and its bight portion is disposed in the space between the
shaft and the rotor.
The annular permanent magnet 32, which is of course
vide a support for the fuel burner 14.
The ?eld means 19' may comprise an annular mag
axially magnetized, may again comprise one of the pole
netically permeable core 31 of substantially U-shaped
cross section having legs 34 and 35 that project radially
pieces 20 of the ?eld means.
It will be apparent that the embodiment of the inven
3,090,875
5
tion just described lends itself readily to an obvious modi
?cation, wherein the fan is omitted, the thermopile is at
tached to the top of the shaft for rotation therewith,
rather than ?xed to the platform, and the rotor disc is
carried by the thermopile. Such a structure would have
disadvantages in the necessity for dynamically balancing
the thermopile, but it would have advantages in affording
good cooling of the cold junctions of the thermocouples.
brushes in axially aligned pairs, engaging the opposite
rotor faces, is for the purpose of doubling the brush con
tact area and IthU‘S reducing the brush resistance to half
of what it would be if brushes were used at only one face
of the rotor. Preferably each brush has a width cir
cumferentially of the rotor which is at least equal to that
of a spoke-like conductor, so that as the spoke-like con
ductors pass in engagement with it the brush is always
In the embodiment of the invention illustrated in FIG
well supported by the conductor that is leaving engage
URES 3, 4 and 6, the motor is of a novel type which 10 ment with it until it is well supported by the conductor
possesses marked advantages over the homopolar motor
that is entering engagement with it. Hence the spaces
in lightness, low cost and e?iciency, and which is substan
between conductors at their inner ends need not be ?lled
tially cheaper and more compact than conventional motors
with insulating material to insure smooth passage of the
suited for low voltage D.C. operation.
brushes from one conductor to another. The brushes
For use with motors of the type illustrated in FIG 15 may be mounted in suitable brush holders 238 carried
URES 3, 4 and 6‘, a series connected thermopile of the
by insulating supporting members 153 secured to the ad
type shown in FIGURE 5 is preferred, since it has sub
jacent ?eld means cores. The pair of ‘brushes 121 asso
stantially higher voltage output. The radially disposed
spoke-like elements 49' alternate circumferentially around
the thermopile between P and N type thermoelectric ma
terials, so that all of them are adapted to have hot junc
tions at their inner ends and cold junctions at their outer
ciated with one of the pole pieces is connected, by means
of a conductor 117, with one terminal T of the thermo
pile, while the other pair of brushes 221 is connected by
a conductor 217, with the other terminal T’.
The ?eld means produce a magnetic ?ux across the air
‘gap which extends a sufficient distance circumferentially
of the rotor as to be linked with each spoke-like conduc
members 49’ are connected in pairs at their inner ends 25 tor at its side ‘of the rotor at all times that such conductor
by ring segments 48' and are connected in other pairs at
is engaged by a brush, or in other words, a spoke-like
their outer ends by segments 59', so that the current path
‘conductor is not contacted by a pair of brushes until it
through the thermopile zigzags inwardly and outwardly.
has entered the ?ux ?eld, and is disengaged ‘from the
The terminals T, T’ are preferably at the outer circum
pair of brushes before it passes out of the flux ?eld.
ference of the thermopile. The inner segments 48' may
As each spoke-like conductor 42 moves angularly into
be circumferentially extended to some extent, as shown,
engagement with a pair of brushes, a diametrically oppo
and provided with heat collecting ?ns 51', and the outer
site spoke-like conductor is also being engaged by the
segments may be similarly extended and provided with
ends, and radially outward heat ?ow will produce the
proper polarities for a series connection. The spoke-like
other pair of brushes. The i?ow of current through the
cooling ?ns 13. Obviously insulating ?llers could be
interposed between adjacent ends of the segments of the 35 rotor is from one pair of brushes 121, outwardly through
the spoke-like conductors engaged ‘by said brushes, then
inner and outer rings to form them into unbroken rings
circumferentially around the rim portion 41 of the ro
for the better guidance of hot gases and cooling air.
tor and inwardly along the diametrically opposite spoke
The motor in this embodiment of the invention fea_
like conductors to the pair of brushes 221 engaged with
tures a rotor 218 which may be formed as a unitary stamp
ing of conductive material such as copper or aluminum
and which is engaged by the brushes near its axis so that
the latter.
The ?eld means have their ?ux ?elds across
the air gaps oriented in axially opposite directions, and
since current is ?owing in radially opposite directions in
the brushes produce relatively little friction drag. The
the spoke-like conductors respectively engaged by the two
rotor 218 comprises an outer annular rim portion 41 and
pairs of brushes, the ?ux ?elds around the energized
a plurality of spoke-like conductors 42 that extend ra
dially inwardly from the rim portion, terminating near 45 spokealike conductors, due to the cturent through them,
react with the ?ux ?elds through the air gaps to produce
the shaft. The inner end portions of the conductors 42
rotation of the rotor in the direction determined by
are circumferentially spaced apart by small distances
and the conductors are thus insulated from one another
except at their outer ends, which have a common con
Pleming’s rule; i.e., using the left hand and pointing the
index ?nger in the direction of ?ux across an air gap and
nection through the rim portion of the rotor, being,7 pref
erably integral with the rim portion. The spoke-like
the middle ?nger in the direction of current through the
conductors have their inner ends clampingly con?ned be
dicate the direction of force and therefore of rotor mo
tion.
intersecting spoke-like conductor 42, the thumb will in
tween insulating washers 43 which also serve to fasten
To prevent the rotor from contacting the pole pieces
the rotor onto the shaft 10.
Instead of an annular ?eld, as in the previously de 55 as a result ‘of vibration ‘or gyroscopic force, rubbing
blocks 47 of nylon, or of graphite insulated from the mo—
scribed embodiments of the invention, the motor here un
der consideration has circurnferentially spaced apart ?eld
means 219 providing a plurality of axially extending
air gaps which are intersected by the rotor. Speci?cally,
the ?eld means may consist of two magnetic yorkes lo
cated diametrically opposite one another, each compris
ing a U-shaped core 331, the legs 234- and 235 of which
embrace the rotor, and each having either permanent
magnet means or electromagnet means to provide a ?ux
?eld which extends axially through its air gap. In the
version shown in FIGURES 3 and 4 permanent magnets
232 of alnico or the like, magnetically oriented axially,
are secured to the inner faces of the legs 234 and 235
of the core and provide the pole pieces 20 at opposite
sides of the air gap.
The brushes 12,1 and 22.1 are mounted in pairs, with
each pair radially in line with one of the ?eld means
tor circuits, may be mounted adjacent to the pole pieces
29. These rubbing lblocks provide rotor engaging sur
‘faces 48 that face the opposite faces of the rim portion
of the rotor and lie in planes intermediate the planes of
the pole pieces and of the faces of the rotor when the
iatter is at rest. Hence the rubbing blocks are engaged
by the rotor only when the latter is in some way dis
torted out of normal ?atness, so that the rubbing blocks
do not impose a constant friction load upon the rotor.
The embodiment of the invention shown in FIGURE 6
is similar to that just described except that the ?eld
means 319 comprises wound electromagnets 332. In this
instance the core 431 of each ?eld means is substantially
C-shaped, and a pair of windings 49 and 49’ embrace
and with the individual brushes comprising each pair
its short inwardly extending legs ‘62 ‘and 63 coaxially with
one another. The opposing inner ends of the legs provide
the pole pieces 20, which face opposite surfaces of the
engaging opposite faces of the rotor at the inner ends of
rotor. The windings 49 and 49' of each ?eld means are
the spoke-like conductors 42. The mounting of the 75 connected in series with one another and with the termi
3,690,875
nals of a battery 64, with a thermoelectric generator, or
with some other low voltage source of E.M.F. In some
cases a motor of this invention having wound ?eld mag
nets would compare fairly well in efficiency with one hav
ing permanent magnet ?elds, such as that illustrated in
FIGURE 3, and would be less expensive to manufacture.
From the foregoing description taken together with the
accompanying drawings it will be apparent that this in
vention provides a light, compact, efficient and inexpensive
therethrough in directions substantially radially of the
rotor.
S. The prime mover of claim 4, further characterized
by the fact that said rotor disc has a circumferentially
continuous conductive peripheral portion, and said sub
stantially radially extending conductor surfaces comprise
spoke-like conductors electrically connected with and ex
tending radially inwardly from said peripheral portion of
the disc but otherwise insulated from one another; and
thermoelectrodynamic prime mover, comprising a ther 10 further characterized by the fact that the brushes engage
the inner end portions of said conductors so that current
rnopile, a heat source for heating the hot junction of the
?ows from one brush to another radially outwardly along
thermopile, a motor which is particularly adapted to be
the conductor engaged by said one brush, around a part
powered by low voltage
from the thermopile, and
of said conductive peripheral portion of the disc, and
a fan driven by the motor for cooling the cold junction of
radially inwardly along the conductor engaged by said
the thermopile, and wherein low voltage output of the
other brush.
thennopile poses no substantial electrical transmission
6. An electric motor adapted to be energized by low
problem because the compactness of the arrangement per
voltage direct current, comprising: a disc-like rotor hav
mits the use of very short conductors. It will also be
ing a circumferentially continuous rim portion of elec
apparent that the invention provides a novel electric
trically conductive material and a plurality of spoke-like
motor adapted to be powered by electric current from a
conductors electrically connected with the rim portion and
low-voltage source and which combines good efficiency
extending substantially radially inwardly therefrom, said
and great compactness with low cost and simplicity.
conductors being electrically insulated from one another
What is claimed as my invention is:
1. A prime mover comprising: an electric motor having
an upright shaft; means providing a heat source substan
tially on the axis of the motor shaft and axially spaced
to one side of the motor; a substantiaily annular thermo
pile electrically connected with the motor and axially
spaced to said one side of the motor with its hot junc
tions disposed near the axis of the motor shaft to be
exposed to heat from said source thereof and its cold
junctions spaced outwardly of said axis from the hot
junctions; and a fan driven by the motor, coaxial with the
motor shaft and axially intermediate the motor and the
thermopile, for moving cooling air across the cold junc
tions of the thermopile.
2. A prime mover of the type comprising means de?n
ing a heat source, thermocouple means having hot junc
tions adapted to be heated by heat from said source and
cold junctions adapted to be maintained at a substantially
lower temperature than the hot junctions to cause current
to ?ow in the thermocouple means, and an electric motor
electrically connected with said thermocouple means, said
prime mover being characterized by: the fact that the
motor has its shaft upright and substantially coaxial with
at their inner ends; means mounting the rotor for rotation
about its axis; a plurality of magnet means mounted at
circumferentially spaced intervals around the rotor and
each having a pair of pole pieces overlying opposite faces
of the rotor and cooperating to de?ne an axially extend~
ing air gap which is intersected by the rotor; and a plu
rality of brushes ?xed with respect to the rotor and
engaging the same at circumferentially spaced intervals
therearound, near the radially inner ends of the spoke
like conductors, said brushes being connectable with the
terminals of a current source and cooperable with one
another and the rotor to conduct a ?ow of current radial
ly outwardly through a conductor engaged by one brush,
around a part of the rim portion of the rotor, and radially
inwardly through a conductor engaged by another brush.
7. An electric motor adapted to be energized by direct
current, of the type having a disc-like rotor mounted for
rotation on its axis, magnet means with pole pieces over
lying opposite faces of the rotor and de?ning axially
extending air gaps intersected by the rotor, and brushes
connectable with a source of current and engaged with
45 the rotor to send current substantially radially there
through: said motor vbeing characterized by the fast that
said means de?ning a heat source and disposed axially to
its rotor has a circumferentially continuous peripheral
one side thereof; further by the fact that said thermo
portion of conductive material and a plurality of spoke
couple means has its hot junctions disposed near the axis
like conductors extending radially inwardly from said
of the motor shaft and adjacent to the heat source, to be
peripheral portion and electrically connected therewith
exposed to heat from said source, and has its cold junc
but being otherwise insulated from one another; and
tions spaced radially outwardly of the motor shaft axis
further characterized by the fact that the brushes are so
from its hot junctions; and further by a fan coaxially
disposed as to contact the rotor at the inner end portions
driven by the motor and axially intermediate the motor
of the spoke-like conductors at circumferentially spaced
and the thermocouple means, for moving cooling air
55 apart locations, so that current ?owing ‘from one of said
across the cold junctions of the thermocouple means.
brushes to the other through the rotor ?ows radially out
3. The prime mover of claim 2 further characterized by
wardly through a conductor with which said one brush
the fact that the motor is of the type having a substan
is engaged, around a part of the peripheral portion of
tially flat, disc-like rotor and magnetic pole pieces overly
the rotor, and radially inwardly along a conductor with
ing opposite faces of the disc.
which the other brush is engaged.
4. A prime mover of the type comprising a heat source, 60
8. The electric motor of claim 7, further characterized
thermocouple means having hot junctions exposed to heat
at said source and cold junctions located in a zone of sub
stantially lower temperature, and an electric motor con
nected with the thermocouple means to be energized by
by the fact that the conductive peripheral portion of the
rotor and the spoke-like conductors thereof are integral
with one another.
9. The electric motor of claim 7, further characterized
by the fact that the peripheral portion of the rotor and
ference between the junctions of the thermocouple means,
the spoke-like conductors are formed as integral parts of
said prime mover being characterized by the fact that:
of a unitary stamping of conductive sheet material.
the motor is of the type comprising a disc like rotor hav
10. The electric motor of claim 7, further character
ing substantially radially extending conductor surfaces,
ized
by the fact that said magnet means comprises perma
magnet means having pole pieces at opposite faces of 70 nent magnets.
the rotor de?ning an axially extending air gap through
11. The electric motor of claim 7, ‘further character
which the rotor disc extends transversely, and brushes
ized by the fact that each of said magnet means com
connected with the thermocouple means and engaging the
prises: a core having an axially extending member ?xed
rotor to contact said conductor surfaces and send current 75 outside the periphery of the rotor, arms extending from
current ?owing as a consequence of the temperature dif
3,090,875
10
said member substantially radially inwardly over oppo
site faces of the rotor disc, and pole pieces on said arms
facing the rotor disc; and windings on said core adapted
to be energized by direct current from a source thereof.
12. An electric motor adapted to be energized by direct
current from a source thereof from which a large cur
rent is available at low voltage, said motor comprising:
a disc-like rotor having a plurality of spoke-like substan
tially radially extending conductors, all connected to one
around the peripheral conductor, and radially inwardly
along the conductor engaged by another brush.
13. The motor of claim 12, further characterized by
the fact that said ‘disc-like rotor comprises a unitary mem
ber having the radially extending conductors and the pe
ripheral conductor integral with one another.
14. The motor of claim 13, further characterized by
rubbing blocks of low friction material ?xed adjacent to
each of the magnet means and having opposing surfaces
another at their outer ends by a peripheral conductor but
otherwise insulated from one another; means mounting
said rotor for rotation on its axis; a plurality of magnet
means mounted at ?xed circumferentially spaced locations
normally slightly spaced from the opposite surfaces of
around the rotor axis and each having pole pieces that
pole pieces.
closely ?atwise overlie opposite faces of the rotor to
de?ne an axially extending air gap transversely inter
sected by the rotor; and a plurality of brushes connect—
able with a low voltage high current DC source, mounted
at circumferentially spaced apart locations around the 20
rotor axis and engaging the inner ends of the spoke-like
conductors to cause current to ?ow radially outwardly
through a conductor engaged by one brush, partway
the rotor, near the periphery of the rotor, to be engaged
by the rotor and thus con?ne the same against excessive
axial displacement at the locations where it passes through
the air gaps to thereby prevent it from rubbing on the
References (Iited in the ?le of this patent
UNITED STATES PATENTS
496,514
2,961,474
Pritsche ______________ __ May 2, 1893
Fritts ________________ __ Nov. 22, 1960
OTHER REFERENCES
Electronics, March 20, 1959, pages 70-73.